During the Disney Interactive presentation at D23 Expo 2015, the team at Disney Infinity revealed that the Keyblade will be the the Ultimate Unlock in Disney Infinity 3.0. The Ultimate Unlock is achieved by collecting every figure available for Disney Infinity. This gives players the opportunity to use the Keyblade as a weapon in the game.
Additionally, fans attending D23 were rewarded a King Mickey costume, which is Mickey Mouse's attire from the Kingdom Hearts series. This costume will NOT be sold in stores.
Here are some pictures of the King Mickey power disk thanks to @WDWNT
Additionally, an image of the Ultimate Unlock Keyblade in Disney Infinity 3.0 can be seen below thanks to KH13 Archives Team member WakelessDream as well as an image of King Mickey's new outfit in Disney Infinity 3.0 thanks to @ThePirateSteven.